To protect the contact circuits of the vehicle's electrical equipment, various combinations of fuses, fuse links and circuit breakers are used, most of which are concentrated in two mounting blocks (see Specifications).
Each individual fuse is used to protect a specific electrical circuit or several circuits at once. A label with an identification card of the location of the fuses in the mounting block is usually glued to the cover of the latter, on its inner side.
The fuse boxes contain compact fuses with bayonet terminals that can be easily removed from their sockets in the box with your fingers if necessary. If any of the power consumers fails, the condition of the corresponding fuse should always be checked first. Turn the ignition key to the ON position and probe the open terminals of each fuse with a test lamp. If the lamp lights up when connected to each terminal, the fuse is OK. If voltage is present only on the power supply side, the fuse has blown. Note also that the fuse body is usually made of transparent plastic, through which the condition of the working jumper can be easily determined.
The fact that the contact jumper of a failed fuse has burned out can be easily detected by visual inspection of its translucent body
When replacing a blown fuse, make sure that the replacement fuse you install matches the type of the element that has failed. Fuses rated for different current ratings may not physically differ from each other, but they are not interchangeable. Each electrical circuit has different operating parameters and requires a different degree of protection, so replacing a fuse (designed for a certain current strength) that does not correspond to its parameters is fraught with the most serious consequences (until a fire breaks out). Operating parameters of the fuse (rated current) usually marked on its plastic body.
Article text obtained from the website mercedesman.ru
If the new fuse also fails immediately after installation, there is no point in replacing it further - first you need to identify and eliminate the cause of the overload in the circuit. In most cases, this is a short circuit in the connecting wiring caused by damage to its insulation.